Many attempts have been made to devise climbing or push-off aids embossed or stamped in the base coating or base layer of skis, which would provide not only the optimum harmony between push-off and gliding behavior and sufficient lateral guidance and smoothness when skiing over hard, grooved tracks but also be producible economically and permit economic production of the embossing or stamping tools required.
Austrian Pat. No. 291 063, which corresponds to U.S. Pat. No. 3,408,086, discloses a step arrangement, including rows of steps extending transversely and having arcuate edges, the individual arc sections being directly contiguous, and rows of steps arranged one behind the other and being laterally offset, preferably by half the step width. This arrangement has the disadvantage of having acute angle corners between the arcuate sections in which snow and ice may accumulate thus reducing the push-off capability accordingly. Moreover, there are no push-off edges which extend at right angles to the push-off direction so that the optimum transmission of the push-off forces is not obtained. Although guidance against lateral slip-off is given, it is available only until the corners mentioned have become filled with snow.
DE-OS No. 29 27 756 discloses a step arrangement having rectilinear step edges perpendicular to the push-off direction, and step flanks at flat angles formed of concave or convex surface sections of overlapping surfaces of revolution. This arrangement has no acute angle intersections in which snow could become stuck. Moreover, the resulting undulated transverse profile affords sufficient lateral guidance. However, as the step ramps which are inclined at flat angles are sections of surfaces of revolution, all gliding faces are curved in transverse direction and, therefore, do not provide optimum support on the track. This is felt as worse gliding behavior, particularly on soft tracks. Besides, it results in uneven wear because surface area parts project even if the curvatures or intersections are very flat.
Swiss Pat. No. 189 670 discloses a ski provided with a base coating which comprises an arrangement of embossed fields of parallelogram shape serving as a push-off aid and being defined by two intersecting families of parallel edges extending at an angle of less than 90.degree. with respect to the longitudinal axis of the ski. The diagonals of these fields extend in longitudinal direction of the ski so that the push-off edges disposed obliquely to the longitudinal direction of the ski intersect at acute angles. It is known from experience that such intersections fill up easily with ice or snow, whereby the push-off effect is reduced accordingly. As no push-off edge is disposed transversely of the push-off direction, the push-off which can be transmitted is not the best.
Austrian Pat. No. 348 386 discloses a base coating having an embossed profile which consists of fields, similar to those according to Swiss Pat. No. 189 690, which are defined by a plurality of intersecting families of parallel delimitation lines. Although several characteristic differences exist with respect to Swiss Pat. No. 189 690, the disadvantages mentioned still persist.
DE-AS No. 22 43 229, which corresponds to U.S. Pat. No. 3,858,894, discloses a base design for cross-country skis which consists of a pattern of scale-like projections protruding from the base surface. At least some of these projections have straight edges at their sides, and at least one of these edges is inclined at an angle with respect to the longitudinal axis of the ski and one edge extends transversely of the longitudinal axis of the ski. The individual projections of a transverse row are separated from one another by narrow, acute angle depressions which may become filled with snow or ice and thus become ineffective. A specific method and a relatively complicated tool are required for manufacture of this base. Besides, projections which protrude beyond the base surface require particular measures to be taken in the manufacture of the ski.
German utility model DE-GM No. 7 831 297, finally, discloses a base coating having an embossed push-off aid which consists of a plurality of steps having steep gradient push-off flanks in push-off direction and flat angle ramps in gliding direction, the upper side of the steps being formed of a continuous honeycomb arrangement of equilateral or biaxially symmetric hexagonal fields.
This known base coating makes allowance for the recognition that, as a rule, the gliding times are much longer than the braking times. This is accomplished in that the overall length available per step is divided in corresponding proportions into a gliding zone and a climbing zone. Yet as the proposed arrangement of the hexagon fields is such that the tips are oriented either to the front or to the rear, again there is the risk that snow and ice will accumulate in the corners between two adjacent steps.
It is another disadvantage of the arrangement described of the hexagon fields that only push-off edges are provided which are inclined with respect to the push-off direction, and this has the consequence of reduced push-off effect. Furthermore, the guide bars provided in the known base coating and extending in skiing direction between two adjacent hexagon fields each, require extremely expensive embossing tools, and it is doubtful if such increased expenditure is worthwhile when considering the effect of the guide bars.
It is, therefore, an object of the present invention to provide a ski base coating in which a push-off aid is embossed to guarantee the optimum transmission of push-off forces and good lateral guidance. It is another object of the invention to provide a ski base coating of such kind that any plugging of the effective steps by ice and snow is substantially reduced. Moreover, it is an object of the invention to provide a kind of base coating for skis which permits simple and economic manufacture of the embossing tool used.